This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-020292, filed Jan. 28, 2000; and No. 2000-160190, filed May 30, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a semiconductor device incorporating a semiconductor chip mounted on a wiring board, a stacked-type semiconductor unit having a plurality of semiconductor devices stacked on a base board, and a method for manufacturing the same.
In recent years, a small memory card on which a flash memory is mounted is utilized in portable information equipment, for example, a digital still camera or a portable information terminal. The market of such a memory card has rapidly been expanded. In particular, the memory cards have been dominating in the field of the digital camera, and will supersede MDs (Mini Disks) and floppy disks.
With the above situation as a background, it is required that a small memory card including only flash memories be larger in capacity, smaller in size and weight, and lower in cost. For this purpose, various package structures and mount structures of a memory IC have been considered.
In general, a thin mold package, such as a TSOP (Thin Small Outline Package), is soldered to a base board, or a bare chip is directly connected to a base board by means of wire bonding or flip-chip bonding. Since the capacity of the given area is determined by a chip size, in order to increase the capacity, a stacked-type semiconductor unit has been required. This type of semiconductor device has a mount structure in which chips are stacked three-dimensionally in order to the overall size of the device or the pitch of the chips.
FIG. 29 shows a conventional stacked-type semiconductor unit. The stacked-type semiconductor unit has a plurality of, for example, four semiconductor devices 20 stacked one on another. Each semiconductor device 20 has a wiring board 24 including a sheet-like holding member 21 made of polyimid or the like and a wiring pattern 22 formed thereon. Bumps 23 made of gold or the like are formed on the wiring pattern 22. A semiconductor chip 1 is mounted on the bumps 23 by flip-chip bonding. The semiconductor chip 1 is sealed with resin 7, such as epoxy, and packaged.
The four semiconductor devices 20 each formed by packaging the semiconductor chip 1 are stacked and mounted on desired connecting lands 8 on a base board 3 via solders 25, for example, solder balls. Each solder 25 is provided on an electrode 26 formed in an end portion of the wiring board 24.
The solders 25 are formed on the electrodes 26 on the wiring board 24 by providing a solder ball or printing solder paste on the electrodes 26. In either case, to firmly and stably connect the stacked wiring boards 24, i.e., the semiconductor device 20, to the base board 3 by the solders 25, it is necessary to supply the solders 25 on the electrodes 26, and thereafter to put the stacked four wiring boards 24 into a reflowing furnace, so that the solders 25 can be melted and fixed to the electrodes 26.
However, when a plurality of semiconductor devices 20 are put in the reflowing furnace to fix the solders 25, the wiring boards 24 may be warped by the influence of heat in the furnace. In addition, the connecting portion between the semiconductor chip 1 and the wiring pattern 22 may be damaged. As a result, defectives may exist in the semiconductor devices 20, resulting in the decrease in manufacturing yield. Moreover, it is difficult to manage the process.
An object of the present invention is to provide a semiconductor device, a stacked-type semiconductor unit, which can be manufactured by a simple process and the quality of which can be stable, and a method for manufacturing the same.
According to a first aspect of the present invention, there is provided a semiconductor device comprising:
a semiconductor chip having flexibility and including an internal electrode;
a wiring board having flexibility and including a wiring pattern electrically connected to the internal electrode of the semiconductor chip; and
an external electrode provided in an end portion of the wiring board and electrically connected to the wiring pattern.
According to another aspect of the present invention, there is provided a stacked-type semiconductor unit having a plurality of semiconductor devices stacked on a base board, each comprising a semiconductor chip having flexibility and including an internal electrode; a wiring board having flexibility and including a wiring pattern electrically connected to the internal electrode of the semiconductor chip; and an external electrode provided in an end portion of the wiring board and electrically connected to the wiring pattern, the stacked-type semiconductor unit comprising:
a base electrode formed on the base board; and
solder electrically connecting and fixing the external electrodes of the plurality of semiconductor devices to the base electrode, in a state where the plurality of semiconductor devices are stacked on the base electrode formed on the base board such that the external electrodes of the plurality of semiconductor devices are aligned.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.